What Causes Collection Of Fluid Around Armpits And Breast After Breast Surgery?

Dear Dr, My wife was operated for breast cancer and her right breast was removed in Dec. 2009. After the operation radiation was done for 21+5 days. Since then a light cloured fluid gets collected in the armpit and around the place of the operation.. This has to be drained at the hospital with a syringe etc. There is absolutely no painl anywhere but it gets uncomfortable moving around the arm once enough fluid gets collected. The frequency of visit to the hospital for draining the fluid has gone down from 12-13 days initially to 40-45 days now. The treating doctor is very casual about it. Everytime we ask him as to how long it will take to stop, his simple answer is, Do not worry about it, it will stop automatically. We are getting worried about it and are losing our patient as it is already more than two years now. Kindly advise us what should we do about this. We are really tired of this.